Many pets are very disturbed by the presence of mirrors or other reflecting surfaces where they see their own image. If there were many reflecting surfaces in nature I would think that it would represent a fitness cost to the individual that is constantly scared of its own reflection. So that made me wonder...

How different would have brained animals evolved if there were way more (and better) reflecting surfaces in nature?

$\begingroup$not much difference, the majority of animals don't make much use of their vision sensory....$\endgroup$
– CharonSep 3 '16 at 5:28

$\begingroup$@渡し守シャロン Actually most animal rely primary on sight. Unlike human, they don't ignore other senses. A scentless, electricless reflection seems as fake to them than a black and white photo to us.$\endgroup$
– MadlozozSep 3 '16 at 11:02

3 Answers
3

Many animals which react badly to seeing their reflection are doing so because they do not recognise the reflection is them. Your cat sees itself in the mirror and thinks: Eek! There's a stranger in MY living room!

Smart animals (people, chimps, elephants, parrots) figure out it is themselves they are seeing. Dumb animals will run away or attack it, but eventually work out that the reflection doesn't actually DO anything and ignore it. Really Dumb Animals (Siamese fighting fish?) will just keep attacking it and attacking it...

If the Earth had been covered in mirrors, then natural selection would favour creatures which were Smart or Dumb. Telling the difference between a mirror and a real member of your species will be a very important skill. They Really Dumb ones will go through their (short) lives wasting energy reacting to reflections. They won't have as much resources to dedicate to other stuff like breeding and defence, and will be outcompeted.

Every spring there will be a rash of newborn animals encountering mirrors for the first time, and figuring out what is real and what is a reflection. Much like baby birds have to figure out that glass is transparent but solid.

Meanwhile, predator-prey interactions become... complicated. Prey are going to get adept at using mirrors to spot predators coming. This includes working out that if the tiger is reflected in that mirror there, it means it is really approaching from the west, so you should run east, right past the reflection.

Predators may have to pick routes without mirrors to sneak up on things. Or may exploit the mirrors to startle prey into the waiting teeth of another pack member.

Animal displays will be magnified by mirrors - one peacock will look like a room full of them. So visual displays may become less important. Scent and sound may replace bright feathers, stotting and strutting.

Surface of water count? There is water everywhere and it doesn't need to be a lot to reflect light into your eyes, some animals can identify themselves in mirrors, like elephants, some primates and birds. Maybe those who can develop awareness of the self image has already done it. The primary sense of recognition of a dog is not vision but smell, you mean that if there were more reflective surfaces it could have changed that? I think sound play a bigger role because of predators

I think if mirrors were so prevalent, a lot of processing power would be needed to respond meaningfully to visual information.

The trouble is, since the simplest light-sensitive animals aren't/weren't intelligent enough to do this, I'm not so sure sight would've evolved at all. It's possible that information based on light would so unreliable as to confer no survival advantage at all.

If sight did evolve, it would make sense for it to evolve to use wavelengths that aren't reflected by the mirrors, or perhaps to be sensitive to polarisation (though I don't know how feasible that is in practice, and it would certainly depend on the properties of the mirrors), so it can tell the difference.

In conclusion, I think for the most part things wouldn't be that different. Either sight would evolve to not have to deal with the mirrors, or some other sense (echolocation, perhaps?) would replace sight in nature.